SAN JOSE, Costa Rica (Reuters) - Costa Rican President Oscar Arias has ordered the expropriation of lucrative beach-front land to protect the endangered leatherback sea turtle, the government said on Thursday.

Arias began expropriation procedures for some 30 hectares (74 acres) of land in northwestern Costa Rica, the most important leatherback sea turtle nesting site on the Pacific Rim, Energy and Environment Minister Roberto Dobles said.

"We are only complying with the law that established Las Baulas (national marine park) in 1995," Dobles told Reuters.

Some of the expropriated land owners, mostly Europeans and U.S. citizens, had resisted the expropriation even though the land was made a national park by law in 1995.

Environmentalists hailed the move to protect the turtles, which have been declining in alarming numbers in recent years.

"It will help us to restore the population of leatherback turtles in the Pacific," said Todd Steiner of the San Francisco-based Turtle Island Restoration Network.

Environmentalists say 95 percent of leatherbacks in the Pacific Ocean have vanished in the last 20 years due to human activity like fishing, poaching of their eggs and building near their nests.

Thousands of leatherbacks built nests at the Las Baulas beaches 10 years ago but the number has dropped to below 100 in the last five years.

Leatherbacks, which can reach a shell length of 5.6 feet

and a weight of 1,543 pounds (700 kg), often die after being entangled in fishing lines and nets.